[Calcium permeability of synaptosomes induced by alpha-latrotoxin].

The paper deals with characteristics of ionic alpha-latrotoxin-induced permeability of rat brain synaptosomes. It has been shown that the addition of alpha-latrotoxin to synaptosomes in the Ca2+-containing media resulted in an extensive and rapid uptake of 45Ca2+ in synaptosomes. alpha -Latrotoxin was not able to enhance the 22Na+ and 86Rb+ uptake or efflux in the Ca2+-containing and Ca2+- and Mg2+-free media. The dye di-O-C3 was used to monitor the membrane potential changes as a consequence of alpha-latrotoxin treatment of synaptosomes. It has been found that alpha-latrotoxin increased synaptosomal fluorescence in the Ca2+-containing media, but failed to induce any increase of fluorescence in Ca2+- and Mg2+-free media. It has been also shown that the calcium uptake induced by alpha-latrotoxin depends on free calcium concentration in synaptosomes. Toxin-induced calcium flows are shown to be of the vector character.